Business segment data (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended										12 Months Ended
	Dec. 31, 2012		Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011		Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses											$ 20,079		$ 17,184		$ 17,271
Revenues											158,966		144,080		133,173
Total earnings before income taxes											22,236		15,314		19,051
Total revenues	44,720		41,050	38,546	38,147	37,955		33,739	38,274	33,720	162,463		143,688		136,185
Capital expenditures											9,775		8,191		5,980
Depreciation of tangible assets											5,146		4,683		4,279
Goodwill at year-end	54,523					53,213					54,523		53,213		49,006
Identifiable assets at year-end	361,584					331,546					361,584		331,546		315,632
Total assets	427,452					392,647					427,452		392,647		372,229
Geico [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses											680		576		1,117
Premiums earned											16,740		15,363		14,283
Goodwill at year-end	1,372					1,372					1,372		1,372
Identifiable assets at year-end	30,986					27,253					30,986		27,253		25,631
General Re [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses											355		144		452
Premiums earned											5,870		5,816		5,693
Goodwill at year-end	13,532					13,532					13,532		13,532
Identifiable assets at year-end	30,477					28,442					30,477		28,442		29,196
Berkshire Hathaway Reinsurance and Primary Groups [Member]
Segment Reporting Information [Line Items]
Goodwill at year-end	607					607					607		607
Identifiable assets at year-end	118,819					104,913					118,819		104,913		104,383
Berkshire Hathaway Insurance Group [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses											6,079		4,973		7,158
Revenues											39,019		36,821		35,935
Capital expenditures											61		40		40
Depreciation of tangible assets											57		56		66
Goodwill at year-end	15,511					15,511					15,511		15,511
Identifiable assets at year-end	180,282					160,608					180,282		160,608		159,210
BNSF [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses											5,377	[1]	4,741	[1]	3,611	[1]
Revenues											20,835	[1]	19,548	[1]	15,059	[1]
Capital expenditures											3,548	[1]	3,325	[1]	1,829	[1]
Depreciation of tangible assets											1,573	[1]	1,480	[1]	1,221	[1]
Goodwill at year-end	14,836					14,803					14,836		14,803
Identifiable assets at year-end	56,839					55,282					56,839		55,282		53,476
Finance and Financial Products Reportable Segment [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses											848		774		689
Revenues											4,110		4,014		4,264
Capital expenditures											367		331		233
Depreciation of tangible assets											184		180		204
Goodwill at year-end	1,036					1,032					1,036		1,032
Identifiable assets at year-end	24,412					23,919					24,412		23,919		24,692
Marmon [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses											1,137		992		813
Revenues											7,171		6,925		5,967
Capital expenditures											817		514		307
Depreciation of tangible assets											479		484		507
Goodwill at year-end	814					727					814		727
Identifiable assets at year-end	11,230					10,597					11,230		10,597		10,047
McLane Company [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses											403		370		369
Revenues											37,437		33,279		32,687
Capital expenditures											225		188		166
Depreciation of tangible assets											149		129		129
Goodwill at year-end	705					155					705		155
Identifiable assets at year-end	5,090					4,107					5,090		4,107		4,018
MidAmerican [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses											1,644		1,659		1,539
Revenues											11,747		11,291		11,305
Capital expenditures											3,380		2,684		2,593
Depreciation of tangible assets											1,440		1,333		1,262
Goodwill at year-end	5,377					5,253					5,377		5,253
Identifiable assets at year-end	46,856					42,039					46,856		42,039		40,045
Other Businesses [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses											4,591	[2]	3,675	[2]	3,092	[2]
Revenues											38,647	[2]	32,202	[2]	27,956	[2]
Capital expenditures											1,377	[2]	1,109	[2]	812	[2]
Depreciation of tangible assets											1,264	[2]	1,021	[2]	890	[2]
Goodwill at year-end	16,244	[3]				15,732	[3]				16,244	[3]	15,732	[3]
Identifiable assets at year-end	36,875	[3]				34,994	[3]				36,875	[3]	34,994	[3]	24,144	[3]
Not Allocated to Segments [Member]
Segment Reporting Information [Line Items]
Interest expense											(271)		(221)		(208)
Investment and derivative gains/losses											3,425		(830)		2,346
Identifiable assets at year-end	11,345					7,888					11,345		7,888		7,591
Berkshire Hathaway Reinsurance Group [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses											304		(714)		176
Premiums earned											9,672		9,147		9,076
Berkshire Hathaway Primary Group [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses											286		242		268
Premiums earned											2,263		1,749		1,697
Berkshire Hathaway Insurance Group Investment Income [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses											4,454		4,725		5,145
Interest, dividend and other investment income											4,474		4,746		5,186
Intersegment Eliminations and Other Reconciling Items [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses											(997)		(819)		(358)
Total revenues											$ 72		$ 438		$ 666

[1] From acquisition date of February 12, 2010.

[2] Includes Lubrizol from the acquisition date of September 16, 2011.

[3] Includes Lubrizol, acquired in 2011.